There has been proposed a resistance change memory device, the resistance value of which is reversibly exchanged by applying voltage, current or heat, and one of states with the different resistance values is stored as data. It is noticed that this kind of memory device succeeds to the conventional flash memory. This resistance change memory is suitable for miniaturizing the cell size, and for constituting a cross-point cell array. In addition, it is easy to stack cell arrays.
There have already been proposed by us some three dimensional (3-D) cell array structures of this kind of memory devices. For example, refer to JP 2005-522045A (PCT/JP2003/000155), and JP 2006-514393A (PCT/JP2003/003257).
To make the best use of these properties, besides, to achieve high density and large capacity, it is effective to use such a multi-level data storage scheme that three or more resistance values are assigned to data. However, the resistance value of the variable resistance element in the resistance change memory will be set or reset in accordance with applied voltage or Joule's heat in such a way that, for example, charge movement occurs when the charge is activated to be over a certain potential barrier in the recording layer. Therefore, the data resistance value is statistically indefinite in principle, and specifically it is not easy in a multi level data storage scheme to set one or more medium resistance values between the highest resistance value and the lowest resistance value.